U.S. patent number 10,230,024 [Application Number 15/744,400] was granted by the patent office on 2019-03-12 for optoelectronic component comprising a conversion element, method of producing an optoelectronic component comprising a conversion element, and use of an optoelectronic component comprising a conversion element.
This patent grant is currently assigned to OSRAM Opto Semiconductors GmbH. The grantee listed for this patent is OSRAM Opto Semiconductors GmbH. Invention is credited to David O'Brien, Norwin von Malm.
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United States Patent |
10,230,024 |
O'Brien , et al. |
March 12, 2019 |
Optoelectronic component comprising a conversion element, method of
producing an optoelectronic component comprising a conversion
element, and use of an optoelectronic component comprising a
conversion element
Abstract
A method of producing an optoelectronic component including a
conversion element includes: A) providing a layer sequence having
an active layer, wherein the active layer is configured to emit
electromagnetic primary radiation; B) providing quantum dots,
wherein the quantum dots are functionalized with an organic group
and/or the quantum dots dissolved or dispersed in a first solvent
and/or are present as a powder; C*) providing a mixture including a
precursor of an inorganic matrix material and of a second solvent;
D) mixing the mixture obtained in step C*) with the quantum dots of
step B); E) drying the mixture; and F) sintering the mixture to
form the conversion element.
Inventors: |
O'Brien; David (Bad Abbach,
DE), von Malm; Norwin (Nittendorf, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
OSRAM Opto Semiconductors GmbH |
Regensburg |
N/A |
DE |
|
|
Assignee: |
OSRAM Opto Semiconductors GmbH
(DE)
|
Family
ID: |
56799411 |
Appl.
No.: |
15/744,400 |
Filed: |
August 4, 2016 |
PCT
Filed: |
August 04, 2016 |
PCT No.: |
PCT/EP2016/068670 |
371(c)(1),(2),(4) Date: |
January 12, 2018 |
PCT
Pub. No.: |
WO2017/025437 |
PCT
Pub. Date: |
February 16, 2017 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20180198034 A1 |
Jul 12, 2018 |
|
Foreign Application Priority Data
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|
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Aug 7, 2015 [DE] |
|
|
10 2015 113 052 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
33/505 (20130101); H01L 33/501 (20130101); H01L
33/502 (20130101); H01L 24/42 (20130101); C09K
11/08 (20130101); H01L 2933/0041 (20130101); H01L
2224/42 (20130101) |
Current International
Class: |
C09K
11/56 (20060101); C09K 11/62 (20060101); C09K
11/70 (20060101); C09K 11/54 (20060101); H01L
33/50 (20100101); H01L 23/00 (20060101); C09K
11/08 (20060101); H01L 51/50 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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10 2007 049 005 |
|
Mar 2009 |
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DE |
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10 2012 210 083 |
|
Dec 2013 |
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DE |
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10 2012 210 195 |
|
Dec 2013 |
|
DE |
|
10 2012 212 086 |
|
Jan 2014 |
|
DE |
|
Other References
Spanhel, L., et al., "Semiconductor Clusters in the Sol-Gel
Process: Quantized Aggregation, Gelation, and Crystal Growth in
Concentrated ZnO Colloids", J. Am. Chem. Soc., 1991, vol. 113, pp.
2826-2833. cited by applicant.
|
Primary Examiner: Turner; Brian
Attorney, Agent or Firm: DLA Piper LLP (US)
Claims
The invention claimed is:
1. A method of producing an optoelectronic component including a
conversion element, comprising: A) providing a layer sequence
having an active layer, wherein the active layer is configured to
emit electromagnetic primary radiation, B) providing quantum dots,
wherein the quantum dots are functionalized with an organic group
and/or the quantum dots dissolved or dispersed in a first solvent
and/or are present as a powder, C*) providing a mixture including a
precursor of an inorganic matrix material and of a second solvent,
D) mixing the mixture obtained in step C*) with the quantum dots of
step B), E) drying the mixture, and F) sintering the mixture to
form the conversion element.
2. The method according to claim 1, wherein the mixture includes a
base in step C*) and/or D).
3. The method according to claim 1, wherein the first and/or the
second solvent is selected from the group consisting of water,
methanol, ethanol, n-propanol, i-propanol, n-butanol, and
combinations thereof.
4. The method according to claim 1, wherein step E) is performed at
a temperature of 20.degree. C. to 100.degree. C.
5. The method according to claim 1, wherein the organic group is
selected from the group consisting of alcoholates, phosphonates and
sulfonates.
6. The method according to claim 1, wherein the precursor of the
inorganic matrix material includes a metal salt, and the metal is
selected from the group consisting of zinc, titanium, zirconium,
silicon, germanium, aluminum, lithium, potassium, sodium, calcium,
magnesium, and combinations thereof.
7. The method according to claim 1, wherein the precursor of the
inorganic matrix material is selected from the group consisting of
acetates, thioacetates, thiolates, alcoholates, phosphonates,
dihydrogen phosphates, silicates, hydroxides and combinations
thereof.
8. The method according to claim 1, wherein the precursor of the
inorganic matrix material is selected from the group consisting of
acetates, thioacetates, thiolates, or combinations thereof.
9. The method according to claim 1, wherein the precursors of the
inorganic matrix material are selected from the group consisting of
dihydrogen phosphates and silicates and combinations thereof.
10. A method of producing an optoelectronic component including a
conversion element, comprising: A) providing a layer sequence
having an active layer, wherein the active layer is configured to
emit electromagnetic primary radiation, B) providing quantum dots,
wherein the quantum dots are functionalized with an organic group
selected from phosphonates and sulfonates and/or the quantum dots
are dissolved or dispersed in a first solvent and/or are present as
a powder, C*) providing a mixture including a precursor of an
inorganic matrix material and of a second solvent, D) mixing the
mixture obtained in step C*) with the quantum dots of step B), E)
drying the mixture, and F) sintering the mixture to form the
conversion element.
11. A method of producing an optoelectronic component including a
conversion element, comprising: A) providing a layer sequence
having an active layer, wherein the active layer is configured to
emit electromagnetic primary radiation, B) providing quantum dots,
wherein the quantum dots are functionalized with an organic group
and/or the quantum dots dissolved or dispersed in a first solvent
and/or are present as a powder, C*) providing a mixture including
1) a precursor of an inorganic matrix material selected from the
group consisting of acetates, thioacetates, thiolates, dihydrogen
phosphates, phosphonates, hydroxides and combinations thereof and
2) a second solvent, D) mixing the mixture obtained in step C*)
with the quantum dots of step B), E) drying the mixture, and F)
sintering the mixture to form the conversion element.
Description
TECHNICAL FIELD
This disclosure relates to an optoelectronic component including a
conversion element, a method of producing an optoelectronic
component including a conversion element and use of an
optoelectronic component including a conversion element.
BACKGROUND
Optoelectronic components such as light-emitting diodes (LEDs)
often comprise conversion elements having a converter material.
Converter materials convert the radiation emitted by a radiation
source into a radiation with altered, e.g. longer wavelength.
Compared to conventional converter materials, quantum dots have
numerous advantages. A narrow spectral full width at half maximum
(FWHM) of the emitted radiation can be achieved by quantum dots,
for example. In addition, use of quantum dots allows for varying
the peak wavelength of the emission radiation in a very simple
manner. This makes the quantum dots very interesting, in particular
for the use in solid-body illumination and backlighting displays,
for example. However, quantum dots come with numerous disadvantages
strongly limiting their use in optoelectronic components. Quantum
dots are particularly susceptible to oxygen and humidity, plus,
they are very susceptible to temperatures above 80.degree. C.,
which are generated in optoelectronic components due to the heat
generated by fluorescence, due to the Stoke's shift and
radiation-free relaxation processes. In addition, the quantum dots
must be isolated from one another to prevent energy losses due to
radiation-free processes occurring due to physical contact of the
quantum dots amongst each other. It is known to embed the quantum
dots in organic matrix materials such as in acrylates, for example.
As most of the organic matrix materials are very permeable to
oxygen and moisture, the quantum dots must additionally be shielded
against the environment, which is achieved by applying an inorganic
layer by a CVD method or PVD method, for example. What is
problematic in this case, is that the thermal expansion coefficient
of such inorganic layers remarkably differs from that of the
organic matrix material such that cracks occur already with
slightest temperature variations due to the thermal stress.
Furthermore, organic matrix materials have the disadvantage of a
very low heat conductivity, which lowers the intensity of the
primary radiation by which the quantum dots can be excited. In
particular with very high exciting performances, the quantum dots
degrade very fast due to the generated heat. Therefore, achieving
the desired light yield requires the quantum dots to be distributed
over a relatively large area, which increases the bulk-factor and
costs of such components, however.
It could therefore be helpful to provide an optoelectronic
component with a conversion element having improved properties that
can additionally be produced in a cost-efficient manner.
SUMMARY
We provide a method of producing an optoelectronic component
including a conversion element, including: A) providing a layer
sequence having an active layer, wherein the active layer is
configured to emit electromagnetic primary radiation, B) providing
quantum dots, wherein the quantum dots are functionalized with an
organic group and/or the quantum dots are dissolved or dispersed in
a first solvent and/or are present as a powder, C*) providing a
mixture including a precursor of an inorganic matrix material and
of a second solvent, D) mixing the mixture obtained in step C*)
with the quantum dots of step B), E) drying the mixture, and F)
sintering the mixture to form the conversion element.
We also provide a method of producing an optoelectronic component
including a conversion element, including: A) providing a layer
sequence having an active layer, wherein the active layer is
configured to emit electromagnetic primary radiation, B) providing
quantum dots, wherein the quantum dots are functionalized with an
organic group selected from phosphonates and sulfonates and/or the
quantum dots are dissolved or dispersed in a first solvent and/or
are present as a powder, C*) providing a mixture including a
precursor of an inorganic matrix material and of a second solvent,
D) mixing the mixture obtained in step C*) with the quantum dots of
step B), E) drying the mixture, and F) sintering the mixture to
form the conversion element.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 and 2 show schematic side views of various examples of
optoelectronic components.
LIST OF REFERENCE CHARACTERS
1 Optoelectronic component
2 Layer sequence
3 Conversion element
4 Casting material
3a Quantum dot
5 Carrier
6 Lead frame
7 Bonding wire
8 Housing
DETAILED DESCRIPTION
We provide an optoelectronic component. The optoelectronic
component includes a layer sequence with an active layer configured
to emit electromagnetic primary radiation during operation of the
component. In addition, the optoelectronic component includes at
least one conversion element arranged in the beam path of the
electromagnetic primary radiation. The at least one conversion
element includes quantum dots and an inorganic matrix material. The
quantum dots are distributed in the inorganic matrix material and
configured to at least partially convert the electromagnetic
primary radiation into an electromagnetic secondary radiation
during operation of the component.
The fact that the quantum dots at least partially convert the
electromagnetic primary radiation into electromagnetic secondary
radiation can mean, on the one hand, that the electromagnetic
primary radiation is at least partially absorbed by the quantum
dots and emitted with a wavelength range that is at least partially
different from the primary radiation. Part of the absorbed primary
radiation, however, is emitted in the form of heat by the quantum
dots. The electromagnetic primary radiation and the electromagnetic
secondary radiation may include one or multiple wavelengths and/or
wavelength ranges in a red to ultraviolet wavelength range, in
particular in a visible wavelength range.
The quantum dots at least partially converting the electromagnetic
primary radiation into an electromagnetic secondary radiation can
also mean that the electromagnetic primary radiation is almost
completely absorbed by the quantum dots and emitted in the form of
an electromagnetic secondary radiation and in the form of heat. The
emitted radiation of the optoelectronic component may thus
correspond almost completely to the electromagnetic secondary
radiation. "Almost complete conversion" is to be understood as a
conversion of more than 90%, in particular more than 95%.
The conversion element may include further converter materials.
It is possible for the converter element to emit a mixed radiation
of primary radiation and secondary radiation of the quantum dots,
of primary radiation, secondary radiation of the quantum dots and
secondary radiation of the further converter materials, of
secondary radiation of the quantum dots and secondary radiation of
the further converter materials, which arouses a white-colored
luminous impression to an observer.
"Layer sequence" in this context is to be understood as a layer
sequence including more than one layer, e.g. a sequence of a
p-doped and an n-doped semiconductor layer, wherein the layers are
arranged on top of one another and at least one active layer that
emits electromagnetic primary radiation is contained.
The layer sequence can be formed as an epitaxial layer sequence or
as a radiation-emitting semiconductor chip having an epitaxial
layer sequence, i.e. as an epitaxially-grown layer sequence. The
layer sequence can be formed on the basis of InGaAln, for example.
The InGaAlN-based semiconductor chips and semiconductor layer
sequences are in particular the ones in which the
epitaxially-produced semiconductor layer sequence comprises a layer
sequence of different individual layers containing at least one
individual layer comprising a material of the III-V semiconductor
compound material system IN.sub.xAl.sub.yGa.sub.1-x-yN, with
0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1 and x+y.ltoreq.1.
Semiconductor layer sequences comprising at least one active layer
based on InGaAlN can emit electromagnetic radiation in an
ultraviolet to green wavelength range, for example.
As an alternative or in addition, the semiconductor layer sequence
of the semiconductor chip can be based on InGaAlP, i.e. the
semiconductor layer sequence can comprise different individual
layers, out of which at least one individual layer comprises a
material of the III-V semiconductor compound material system
In.sub.xAl.sub.yGa.sub.1-x-yP, with 0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1 and x+y.ltoreq.1.
Semiconductor layer sequences or semiconductor chips comprising at
least one active layer on the basis of InGaAlP can preferably emit
electromagnetic radiation with one or multiple spectral components
in a green to red wavelength range, for example.
As an alternative or in addition, the semiconductor layer sequence
or the semiconductor chip can also comprise other III-V
semiconductor compound materials, e.g. an AlGaAs-based material, or
II-VI semiconductor compound material systems. In particular, an
active layer comprising an AlGaAs-based material can be suitable to
emit electromagnetic radiation with one or multiple spectral
components in a red to infrared wavelength range.
Besides the active layer, the active semiconductor layer sequence
can include further functional layers and functional regions such
as p-doped or n-doped charge carrier transport layers, i.e.
electron transport layers or hole transport layers, undoped or
p-doped or n-doped confinement, cladding or waveguide layers,
barrier layers, planarization layers, buffer layers, protective
layers and/or electrodes as well as combinations thereof.
Furthermore, one or more mirror layers can be applied on a side of
the semiconductor layer sequence facing away from the growth
substrate. The structures described concerning the active layer or
the further functional layers and regions are known with regard to
design, function and structure and are therefore not explained in
greater detail here.
The heat generated in the conversion element due to the quantum
dots and the layer sequence can be dissipated particularly well by
a conversion element including quantum dots and an inorganic matrix
material. As a result, only a small or negligible heat accumulation
is produced in the conversion element and a constant luminous
intensity and a constant color location can be ensured over the
time of operation of the optoelectronic component. An early failure
of the optoelectronic component can be prevented thereby, and the
service life of the optoelectronic component can be extended. In
addition, it is possible for the quantum dots to be excited by a
primary radiation in a high-power range. Typical, high power
densities of LEDs are in a range of approximately 1.5 W/mm.sup.2
for primary radiation in the blue spectral range, for example, with
the value being considerably higher concerning lasers. The power
density can therefore be greater than or equal to 1.5 W/mm.sup.2.
By a high optical power density, the required area to be irradiated
decreases and therefore the number of light sources (LEDs) as well
as of quantum dots required to achieve a certain light yield.
Furthermore, the conversion element can be produced with
comparatively thin layer thicknesses, which in addition reduces
costs. Moreover, the quantum dots are protected from oxygen and
moisture by the inorganic matrix material.
The inorganic matrix material may have a thermal conductivity of 1
to 50 W/mk. In these ranges, the heat developing by the quantum
dots and the layer sequence can be particularly well dissipated in
the conversion element. The higher the thermal conductivity of the
inorganic matrix material, the better the dissipation of heat.
Compared to organic matrix materials, the thermal conductivity is
significantly increased. As a result, a constant luminous intensity
and a constant color location can be ensured over the time of
operation of the optoelectronic component. In addition, it is
possible for the quantum dots to be excited by a primary radiation
in a high-power range, as the developing heat is very well
dissipated and does not lead to the degradation of the quantum
dots.
The inorganic matrix material or the conversion element may be
transparent to the primary radiation emitted by the active layer of
the layer sequence.
"Transparent" means that a material, a layer or an element is
transmissive for the entire electromagnetic visible spectrum, or is
at least partially transmissive for a sub-spectrum thereof. The
primary radiation emitted by the layer sequence can be in the
visible range of the electromagnetic spectrum, for example.
The conversion element or the inorganic matrix material may be
transparent to the secondary radiation emitted by the quantum dots.
Preferably, the inorganic matrix material has a transparency of
more than 95%. Particularly preferably, the transparency to the
emitted primary radiation and/or the emitted secondary radiation of
the inorganic matrix material is above 98%.
The quantum dots may be material structures in the nanometer range
including 5.times.10.sup.1 to 10.sup.5 atoms, for example.
Quantum dots are very susceptible to oxygen and humidity.
Preferably, the quantum dots are particularly well protected
against such environmental impact by the inorganic matrix material
enclosing them such that the quantum dots exhibit a constant
performance over the time of operation of the component.
The quantum dots may include a II/VI semiconductor or a III/V
semiconductor. The quantum dots are selected from a group including
InP, CdS, CdSe and CuInSe.sub.2, for example.
The quantum dots may have an average diameter of 3 to 10 nm,
particularly preferably of 3 to 5 nm. By variating the size of the
quantum dots, the wavelength of the secondary radiation can be
varied in a targeted manner, and therefore individually adapted to
the respective application.
The quantum dots may have a spectral full width at half maximum,
FWHM for short, of at most 50 nm, particularly preferably of at
most 35 nm. The full width at half maximum is 30 nm, for
example.
The quantum dots may include a core and a shell. In this case, the
core is formed from the mentioned II/VI or III/V semiconductor
compound materials, and it is surrounded by a shell. The core
consists of the mentioned II/VI or III/V semiconductor compound
materials, in particular. The shell can comprise or consist of an
inorganic material. The core and the shell are in direct contact
with each other, in particular.
The inorganic material of the shell can comprise or consist of ZnS
or ZnSe.
The quantum dots may be present in an amount of 1 to 99 vol.-% with
respect to the total amount of quantum dots and inorganic matrix
material. If the conversion element is formed as a plate, the
quantum dots are preferably present in an amount of 90 to 99 vol.-%
with respect to the total amount of quantum dots and inorganic
matrix material.
The inorganic matrix material may be a glass or a ceramic.
The inorganic material of the shell of the quantum dots may be a
part of the ceramic or of the glass of the inorganic matrix
material. This way, the quantum dots are fixedly embedded in the
network of the inorganic matrix material. This allows for the
generated heat to be dissipated very efficiently from the quantum
dots via the matrix material.
The inorganic matrix material may be a metal oxide, a metal
sulfide, a metal silicate and/or a metal phosphate. Preferably, the
inorganic matrix material is a metal oxide, a metal silicate, a
metal phosphate and/or a metal sulfide, particularly preferably a
metal oxide, a metal silicate and/or a metal phosphate.
The metal of the metal oxide, of the metal sulfide, of the metal
silicate and/or of the metal phosphate may be selected from a group
including zinc, titanium, zirconium, silicon, germanium, aluminum,
lithium, potassium, sodium, calcium, magnesium, copper, and
combinations thereof. Preferably, the metal is selected from a
group including potassium, sodium, lithium, zinc, titanium,
zirconium, silicon, aluminum and combinations thereof. Particularly
preferably, the metal is selected from a group including potassium,
silicon, aluminum, zinc and combinations thereof.
The quantum dots may be bound to the inorganic matrix material by
chemical bonds. Preferably, covalent and/or ionic bonds are
concerned here. In particular, the chemical bond is present between
the material of the shell of the quantum dot and the inorganic
matrix material.
The inorganic matrix material may comprise or consist of ZnO, ZnS,
TiO.sub.2, ZrO.sub.2, SiO.sub.2, AlPO.sub.4,
Al(H.sub.2PO.sub.4).sub.3, Al.sub.2(HPO.sub.4).sub.3,
AlH.sub.2P.sub.3O.sub.10, Al(PO.sub.3).sub.3,
[Al(PO.sub.3).sub.3].sub.n, M.sub.4SiO.sub.4, M.sub.2SiO.sub.3,
M.sub.2Si.sub.2O.sub.5 and/or M.sub.2Si.sub.3O.sub.7, with M=Li, Na
and/or K. In these inorganic matrix materials, it can be ensured
that the energy band of the inorganic matrix material is greater
than the energy of the secondary radiation emitted by the quantum
dots. Preferably, the inorganic matrix material includes or
consists of ZnO, AlPO.sub.4, Al(H.sub.2PO.sub.4).sub.3,
Al.sub.2(HPO.sub.4).sub.3, AlH.sub.2P.sub.3O.sub.10,
Al(PO.sub.3).sub.3 and/or K.sub.2SiO.sub.3.
The quantum dots may be distributed in the inorganic matrix
material either homogenously or with a concentration gradient.
The quantum dots may be arranged spaced from one another in the
conversion element. As a result, non-radiating energy losses
produced by the quantum dots physically contacting one another, can
be prevented or largely prevented, respectively.
A protective layer may be arranged above the conversion element.
The conversion element and the protective layer are in direct
contact, in particular. The protective layer includes or consists
of an inorganic material.
A layer or an element being arranged or applied "on to" or "above"
another layer or another element can mean that a layer or an
element is arranged in direct mechanical and/or electric contact on
to the other layer or the other element. Furthermore, it can also
mean that the one layer or the one element is arranged indirectly
on or above the other layer or the other element. Here, further
layers and/or elements can be arranged between the one layer or the
other layer or between the one element or the other element,
respectively.
Due to the fact that the protective layer and the inorganic matrix
material include or consist of an inorganic material, it can be
ensured that the thermal expansion coefficient is the same or
approximately the same. This leads to a uniform expansion of the
materials upon temperature fluctuations and temperature increase,
and can thus not or hardly lead to thermal stress causing
cracks.
The protective layer is applied on to the conversion element by an
atomic layer deposition process, ALD for short, by PVD "physical
vapor deposition" process or by a CVD "chemical vapor deposition"
process. These processes allow for generation of very dense layers
such that the conversion element is once more protected against the
penetration of moisture or oxygen. The protective layer can include
Al.sub.2O.sub.3, SiO.sub.2, TiO.sub.2, Si.sub.3N.sub.4 or zinc tin
oxide. The protective layer includes Al.sub.2O.sub.3 or consists of
Al.sub.2O.sub.3, for example. It is also possible for multiple
protective layers, e.g. of Al.sub.2O.sub.3, to be arranged above
the conversion element.
It is possible for the protective layer to cover the entire surface
of the conversion element facing away from the layer sequence.
The optoelectronic component can include a housing. The housing can
have a recess arranged in the center thereof, the layer sequence
can be attached in the recess. It is also possible for the recess
to be filled with a casting material covering the layer sequence.
However, the recess can consist of an air space as well.
The conversion element may be formed as a plate arranged above the
layer sequence. The plate can be in direct mechanical contact to
the layer sequence or be arranged at a distance thereto.
The layer thickness of the entire plate can be uniform. This allows
to achieve a constant color location over the entire surface of the
plate. The layer thickness is 100 nm to 150 .mu.m, for example.
The plate can be directly attached on to the layer sequence. It is
possible for the plate to cover the entire surface of the
semiconductor layer sequence.
The plate may be arranged above the recess of the housing. In this
example of the conversion element, there is no direct and/or
form-fit contact of the conversion element with the layer sequence.
In other words, there can be a distance between the conversion
element and the layer sequence. In other words, the conversion
element is arranged downstream of the layer sequence and radiated
by the primary radiation. A casting compound or an air gap can be
formed between the conversion element and the layer sequence.
An adhesive layer may be arranged between the layer sequence and
the plate or between the plate and the housing. In addition, an
adhesive layer can be arranged between the plate and the casting
compound.
The fact that a layer or an element "is arranged between two other
layers or elements" can mean, that the one layer or the one element
is arranged in immediate and direct mechanical and/or direct
electrical contact with one of the two other layers or elements and
in direct mechanical and/or electrical contact or electric or in
indirect contact with other layers or other elements. In indirect
contact, other layers and/or elements can be arranged between the
one and at least one of the other layers or between the one and at
least one of the two other elements, respectively.
It is possible for the plate to be produced separately and attached
on to the layer sequence. In this case, an adhesive layer can be
attached on to the layer sequence or the housing to fix the
plate.
The adhesive layer may include SiO.sub.2, Si.sub.3N.sub.4,
Al.sub.2O.sub.3, ITO (indium tin oxide), ZnO or silicone, or
consist of one of these materials.
The plate may be produced directly on the layer sequence or the
housing. This proved to be advantageous in particular with plates
having smaller layer thicknesses.
The conversion element may be formed as a casting compound. The
conversion element can fill the recess in the housing. In this
example, the conversion element covers the layer sequence.
The optoelectronic component can be luminescent diodes,
photodiode-transistor-arrays/modules and/or optical couplers. As an
alternative, it is possible to choose an organic light-emitting
diode (OLED) as the optoelectronic component.
The specified examples of the optoelectronic component can be
produced according to the method indicated below. All features
mentioned in the method can as well be features of the
above-specified examples of the optoelectronic component and vice
versa.
A method of producing an optoelectronic component including a
conversion element is disclosed. The method includes the following
method steps: A) providing a layer sequence having an active layer,
wherein the active layer is configured to emit electromagnetic
primary radiation, B) providing quantum dots, wherein the quantum
dots are functionalized with an organic group and/or the quantum
dots are dissolved or dispersed in a first solvent and/or are
present as a powder, C*) providing a mixture including a precursor
of an inorganic matrix material and of a second solvent, D) mixing
the mixture obtained in method step C) with quantum dots of method
step B), E) drying the mixture, F) sintering the mixture to form
the conversion element.
The precursor of the inorganic matrix material may be selected from
a group including acetates, thioacetates, thiolates, alcoholates,
phosphonates, dihydrogen phosphates, silicates, hydroxides, and
combinations thereof.
Preferably, the method comprises the method steps: A) providing a
layer sequence having an active layer, wherein the active layer is
configured to emit electromagnetic primary radiation, B) providing
quantum dots, wherein the quantum dots are functionalized with an
organic group and/or the quantum dots are dissolved or dispersed in
a first solvent and/or are present in the form of a powder, C)
providing a mixture including a precursor of an inorganic matrix
material and of a second solvent, wherein the precursor of the
inorganic matrix material includes acetates, thioacetates,
thiolates, phosphonates and/or hydroxides, or C') providing a
mixture including a precursor of an inorganic matrix material and
of a second solvent, wherein the precursor of the inorganic matrix
material includes a dihydrogen phosphate and/or a metal silicate,
D) mixing the mixture obtained from method step C) or C') with the
quantum dots of method step B), E) drying the mixture, F) sintering
the mixture to form the conversion element (3).
The mixture in method step C) may include a base. The base is LiOH,
Mg(OH).sub.2, NaOH or KOH. Preferably, the base is LiOH.
The mixture in method step D) may include a base or a further base.
The base is LiOH, MG(OH).sub.2, NaOH or KOH, for example.
Preferably, the base is Mg(OH).sub.2, NaOH or KOH. By adding the
base, the inorganic matrix material precipitates. The inorganic
matrix material in the colloidal form is formed.
In method step C*), a mixture may be provided that includes a
precursor of an inorganic matrix material and of a second solvent,
wherein the precursor of the inorganic matrix material includes a
silicate, preferably K.sub.2SiO.sub.3.
In method step C'), a mixture may be produced, the mixture
including a precursor of an inorganic matrix material and of a
second solvent, wherein the precursor of the inorganic matrix
material includes a silicate and a dihydrogen phosphate. An
inorganic matrix material produced from these precursors
surprisingly exhibits an improved resistance against corrosion and
humidity than matrix materials that are produced only from a
silicate or only from a dihydrogen phosphate.
In method step C'), a mixture including a precursor of an inorganic
matrix material and of a second solvent may be provided, wherein
the precursor of the inorganic matrix material includes or consists
of a metal silicate and a metal dihydrogen phosphate. The metal of
the metal silicate is selected from lithium, potassium, sodium, and
combinations thereof, and the metal of the metal dihydrogen
phosphate is selected from zinc, titanium, zirconium, aluminum,
calcium, magnesium, copper, and combinations thereof. Preferably,
the metal of the metal silicate is potassium, and the metal of the
metal dihydrogen phosphate is aluminum.
The first and/or the second solvent may be selected from a group
including water, methanol, ethanol, n-propanol, i-propanol,
n-butanol, and combinations thereof. Preferably, the first and/or
the second solvent is ethanol.
The organic group may be selected from a group including
alcoholates, phosphonates and sulfonates. In particular, the
organic group is chemically bound to the shell of the quantum dots.
Through a chemical reaction, via the organic groups, the quantum
dots can be bound to the inorganic matrix material. It is also
possible for the organic group to split off and that it is thus no
longer present in the conversion element.
The precursor of the inorganic matrix material may be a metal salt,
wherein the metal salt is selected from a group including zinc,
titanium, zirconium, silicon, germanium, aluminum, lithium,
potassium, sodium, calcium, magnesium, copper, and combinations
thereof.
The precursor of the inorganic matrix material may be selected from
a group including acetates, thioacetates, thiolates, alcoholates,
phosphonates, silicates, dihydrogen phosphates, hydroxides and
combinations thereof. Preferably, the precursor of the inorganic
matrix material is an acetate, thiolate, thioacetate or alcoholate,
particularly preferably an acetate. The precursor of the inorganic
matrix material is an acetate such as zinc acetate, for
example.
The inorganic matrix material in colloidal form is produced in the
first solvent or in the first and second solvent from the mixture
provided in method step C) through a so-called sol-gel process.
Formation of the inorganic matrix material in the colloidal form
takes place at a temperature of 20.degree. C. to 100.degree. C.,
preferably below the boiling point of the first and/or the second
solvent. Formation of the inorganic matrix material in the
colloidal form can also be referred to as sol-gel formation.
The inorganic matrix material may include or consist of ZnO, ZnS,
TiO.sub.2, ZrO.sub.2, SiO.sub.2, AlPO.sub.4,
Al(H.sub.2PO.sub.4).sub.3, Al.sub.2(HPO.sub.4).sub.3,
AlH.sub.2P.sub.3O.sub.10, M.sub.4SiO.sub.4, M.sub.2SiO.sub.3,
M.sub.2Si.sub.2O.sub.5 and/or M.sub.2Si.sub.3O.sub.7, with M=Li, Na
and/or K.
The first and the second solvent may be removed in method step E).
In this case, possible organic by-products such as alcohols or
developing H.sub.2O are removed as well.
Method step E) may be performed at a temperature of 20.degree. C.
to 100.degree. C.
The mixture obtained in method step D) may be applied directly on
to the layer sequence. This way, the conversion element can
directly form on the layer sequence. Advantageously, no adhesive
layer is required between the layer sequence and the conversion
element. In this way, the conversion element in the component is
supported mechanically by the layer sequence and, advantageously,
it is not necessary to apply a so-called "pick and place" process,
i.e. a separate production of the conversion element and subsequent
application on to the layer sequence. In particular with a thin
conversion element, for example, only a few nanometers, this method
provides considerable advantages. In addition, it is possible to
adjust the conversion element directly to the dimensions of the
layer sequence. A subsequent adjustment of the size such as in the
case of producing the conversion element separately, is thus not
necessary.
The mixture obtained in method step D) may be directly applied on
to a casting compound and a housing. The layer sequence is arranged
in the recess of the housing and the recess is filled with a
casting material. Thus, the conversion element can form directly on
the casting compound and the housing, i.e. above the recess of the
housing.
Applying the mixture obtained in method step D) can be effected by
dip-coating, stencil printing, screen printing, ink-jetting,
spray-coating or spin-coating.
Sintering may be performed in method step F) at a temperature of
below 350.degree. C., preferably below 300.degree. C., particularly
preferably below 200.degree. C., for example, 100.degree. C. to
300.degree. C., or 100.degree. C. to 200.degree. C. In particular,
if the sintering of the mixture is effected with this mixture being
applied on to the layer sequence, it can be ensured at these
temperatures that the layer sequence is not damaged at these
temperatures.
The inorganic material of the shell of the quantum dots may become
part of the ceramic or the glass of the inorganic matrix material
by the sintering. In this way, the quantum dots are firmly
integrated in the network of the inorganic matrix material.
The specified examples of the phosphor can be applied to the use
mentioned below. In other words, features of the phosphor and of
the method are thus also disclosed for the use and vice versa.
The use of an optoelectronic component for backlighting
applications is provided. For backlighting applications, a wide
color space must be achieved, that has phosphors narrow-band
emitting red and green, which is possible by the narrow-band
emission of the quantum dots.
The layer sequence as the primary radiation source can emit a
primary radiation with an emission wavelength of 350 to 450 nm, for
example.
In one example of the use, this use relates to display
backlighting.
Further advantages and developments result from the examples
described in the following with reference to the Figures.
Like or equivalent components are indicated with the same reference
characters throughout the figures, respectively. The illustrated
elements and their size ratios amongst one another are not to be
considered true to scale, rather, individual elements, in
particular layer thicknesses, can be illustrated in an exaggerated
size for the purpose of a better understanding.
The optoelectronic component 1 according to FIG. 1 shows a carrier
5 with a lead frame 6. The carrier 5 has a layer sequence 2
arranged thereon, which is electrically-connected to the lead frame
6 via bonding wires 7. The layer sequence 2 has a conversion
element 2 in the form of a plate arranged over it. The conversion
element 3 comprises quantum dots 3a and an inorganic matrix
material, with the quantum dots 3a being distributed evenly
throughout the inorganic matrix material. The inorganic matrix
material consists of ZnO, for example. The quantum dots 3a consist
of CdSe and a shell of ZnS. The inorganic matrix material is a
ceramic, in particular, and due to the production method, the ZnS
of the shell of the quantum dots 3a is part of the ceramic. The
plate is arranged in the beam path of the electromagnetic primary
radiation, which is emitted by an active layer (not separately
illustrated here) in the layer sequence 2. Due to the high thermal
conductivity of the inorganic matrix material, the developing heat
can be dissipated very well in the conversion element 3. As a
result, only a small or negligible heat accumulation forms in the
conversion element 3, and a constant luminous intensity and a
constant color location can be ensured over the time of operation
of the optoelectronic component 1. It is thus possible to excite
the quantum dots 3a with a higher radiation density of the primary
radiation. Accordingly, less quantum dots 3a are required to
achieve a desired light yield. The physical dimension of the
component can thus be kept small and costs can be reduced. In
addition, the inorganic matrix material protects the quantum dots
3a against moisture and oxygen. In this way, an early failure of
the optoelectronic component 1 can be prevented and the service
life of the optoelectronic component 1 can be extended. Plus, the
conversion element 3 is robust against exposure to radiation. It
does not or not significantly become cloudy and does not or not
significantly start yellowing. This ensures that the light yield is
not or only slightly decreased and the emission characteristics of
the optoelectronic components 1 is not or only slightly altered.
The mechanical strength of the conversion element 3, too, can be
maintained despite these stresses at least to a large extent. The
conversion element can have a protective layer (not shown here)
applied on top of it by an ALD process, for example, made of
Al.sub.2O.sub.3. The conversion element can thus be additionally
protected against moisture and oxygen.
In addition, the layer sequence 2 and the conversion element 3 can
have an adhesive layer (not shown here) attached therebetween. The
adhesive layer can include silicone, for example.
The optoelectronic component 1 preferably is a LED, with the
radiation being coupled-out upwards through a transparent
semiconductor layer sequence 2 and the conversion element 3.
The optoelectronic component is, for example, produced as follows:
an ethanolic solution of zinc acetate is added with LiOH, for
example, and subsequently added with an ethanolic solution of
quantum dots, that consist of a CdSe-core and a ZnS-shell. NaOH is
added, forming the inorganic matrix material, i.e. ZnO, in the
colloidal form. The mixture is applied on to a provided layer
sequence. Ethanol and by-products are removed by raising the
temperature up to 70.degree. C., for example. Thereafter, sintering
is performed at a temperature of about 200.degree. C.
The conversion element 3 can alternatively be produced as follows:
an aqueous solution of Al(H.sub.2PO.sub.4).sub.3 is added with
quantum dots in the form of powder, which consist of a CdSe-core
and a ZnS-shell. The mixture is applied on to a provided layer
sequence. After drying, sintering is performed at a temperature of
approximately 300.degree. C. for three hours. The resulting matrix
material includes at least Al(H.sub.2PO.sub.4).sub.3,
Al.sub.2(HPO.sub.4).sub.3, AlH.sub.2P.sub.3O.sub.10 and
Al(PO.sub.4).sub.3.
As an alternative, the conversion element 3 can be produced as
follows: an aqueous solution of K.sub.2SiO.sub.3 and
Al(H.sub.2PO.sub.4).sub.3 is added with quantum dots in the form of
powder, which consist of a CdSe-core and a ZnS-shell. The weight
ratio of K.sub.2SiO.sub.3 and Al(H.sub.2PO.sub.4).sub.3 is 3:1 to
8:1, for example. The mixture is applied on to a provided layer
sequence. After a drying process, sintering is performed for three
hours at a temperature of approximately 150.degree. C. The formed
matrix material includes a potassium silicate and an aluminum
phosphate such as Al(H.sub.2PO.sub.4).sub.3,
Al.sub.2(HPO.sub.4).sub.3, AlH.sub.2P.sub.3O.sub.10 and
Al(PO.sub.4).sub.3.
The optoelectronic component 1 according to FIG. 2 shows a carrier
5 with a lead frame 6 and a housing 8. The housing 8 comprises a
recess in the center, in which the layer sequence 2 is arranged,
which is connected to the lead frame 6 in an
electrically-conductive manner. The recess is filled with a casting
material 4. The casting material 4 includes an epoxy, for
example.
A conversion element 3 is arranged above the recess of the housing
8 and the housing 8. The conversion element 3 is formed in the form
of a plate and arranged in the beam path of the electromagnetic
primary radiation, which is emitted by an active layer (not shown
separately here) in the layer sequence 2.
The conversion element 3 includes quantum dots 3a and an inorganic
matrix material, with the quantum dots 3a distributed in the matrix
material in a homogenous manner, for example. The inorganic matrix
material consists of ZnS, for example. The quantum dots 3a consist
of CuInSe.sub.2 and a shell of ZnS, for example. In particular, the
inorganic matrix material is a ceramic, and due to the production
method, the ZnS of the shell of the quantum dots 3a is part of the
ceramic. The Zns can be produced from an ethanolic solution of zinc
thioacetate and LiOH.
In addition, an adhesive layer (not shown here) can be attached
between the housing and the conversion element 3 and between the
casting compound 4 and the conversion element 3. The adhesive layer
can include silicone, for example.
Preferably, the optoelectronic component 1 is a LED, wherein the
radiation is coupled-out upwards through a transparent
semiconductor layer sequence 2, a transparent casting compound 4
and the conversion element 3.
Our components and methods are not limited to the examples by this
description. Rather, this disclosure comprises any new feature as
well as any combination of features, which in particular includes
any combination of features in the appended claims, even if the
feature or combination is per se not explicitly indicated in the
claims or the examples.
This application claims priority of DE 10 2015 113 052.1, the
subject matter of which is incorporated herein by reference.
* * * * *